Although the quest chain can no longer be started, players on the quest [60R] Atiesh, the Befouled Greatstaff (or any later quest in the chain) who already have the [Staff Head of Atiesh] can still complete the legendary quest chain and get the Feat of Strength. This requires first collecting 40 [Splinter of Atiesh], begining the quest chain, and killing Kel'Thuzad in the original 40-man version of Naxxramas. If these requirements have been met, the rest of the quest chain is still completable.